Comments, observations and thoughts from two left coast bloggers on applied statistics, higher education and epidemiology. Joseph is a new assistant professor. Mark is a marketing statistician and former math teacher.

Friday, October 26, 2012

Andrew Gelman spends some time on this latest quote from Steven Levitt on the rationality of voting:

DUBNER: So Levitt, how can you in your life, when you wander around, tell the difference between a smart person and a not-so-smart person?

LEVITT: Well, one good indicator of a person who’s not so smart is if they vote in a presidential election because they think their vote might actually decide which candidate wins. . . . there has never been and there never will be a vote cast in a presidential election that could possibly be decisive.

Gelman has been riding this beat for a long time, repeatedly pointing out the flaws in this strangely persistent argument. He makes a good case (part of which I basically paraphrase in point one), but there are other problems with Levitt's claims.

Here's a brief and certainly incomplete list of objections.

1. Every vote affects the probability distribution of a race, and since the difference in outcomes is so large, even a tiny change in probabilities can conceivably create a detectable change in expected value

2. Every vote in every race. Except for undervoting, we're talking about the combined impact for the entire ballot.

3. This isn't binary. The margin of a win can affect:

Perceived mandate and political capital;

Officials' decisions (particularly in non-term-limited positions). Congressmen who win by large margins are less likely to feel constrained about unpopular votes;

Funding. A lopsided defeat can make it harder for a candidate or a state party to raise money;

Party strategy. How much effort do you expend finding a challenger against an official who beat you by more than ten points last time?;

Media narrative.It's possible to come back after press corp has labeled you a loser, but it isn't easy.

and finally

4. The system works better with higher response rates. It's more stable and harder to game. Perhaps even more important, it does a better job representing the will of the governed.

That's the top of my head list. Undoubted, I missed some.

Gelman goes on:

I would not conclude from the above discussion that Levitt is not so smart. Of course he’s very smart, he just happens to be misinformed on this issue. I applaud Levitt’s willingness to go out on a limb and say controversial things in a podcast, to get people thinking. I just wish he’d be a bit less sure of himself and not go around saying that he thinks that Aaron, Noah, Nate and I are not so smart.

He's being overly diplomatic. Levitt isn't just misinformed; he's willfully misinformed. In issue after issue (drunk driving, car seats, solar energy) he has used sloppy reasoning to reach a controversial position, then has done his best to turn a deaf ear to those who pointed out his errors. We did get a partial retraction of his claims on driving*, but on others he has doubled down and occasionally resorted to cheap shots at those who disagreed with him.

Levitt is very smart. That's what makes this sort off thing so difficult to overlook.

* Though still leaving potential errors unacknowledged, such as the likely possibility that drivers in accidents are more likely to be checked for intoxication than pedestrians, that a stricter standard might be used, that many of the most intoxicated are prevented from driving and that intoxication is more likely to be noted in official records for drivers